Go to
http://www.symantec.com and run their free scanner from THEIR system to be abSOlutely sure. A virus scan running from a seperate system can't be spoofed by virii like a scan from the HD its examining...
Takes some time for it to run and you are basically down while it runs since it might restart if you keep trying to work, but well worth the peace of mind. We run it monthly and it takes hours with all the gigs of HD we have. We do sleep well knowing it double checks our AV on the systems.
